Transmission device and automatic gain control method

ABSTRACT

A transmission control section  101  temporarily stores a transmission signal, outputs the stored transmission signal to a coding section  102  and outputs transmission timing information to a counter section  107 . A preamble insertion section  104  inserts AGC preambles corresponding to the number set by a preamble number control section  110  into the transmission signal. The preamble number control section  110  compares a transmission time interval input from a subtraction section  109  with a threshold, decides to insert ten AGC preambles into the transmission signal when the transmission time interval is equal to or greater than the threshold and decides to insert five AGC preambles into the transmission signal when the transmission time interval is smaller than the threshold. By so doing, it is possible to make the transmission efficiency compatible with the error rate characteristic.

TECHNICAL FIELD

The present invention relates to a transmission apparatus and auto gaincontrol method, and more particularly, to a transmission apparatus andauto gain control method for transmitting a transmission signalincluding auto gain control preambles.

BACKGROUND ART

In a wireless communication system such as wireless LAN, a user is notalways transmitting/receiving signals at a location with a constantreception level and the level of a signal received varies from one userto another, for example, the distance from a transmission antenna may belong or may be short. Therefore, suppressing the level of a receivedsignal to within a dynamic range of an analog/digital converter is atechnology essential to a wireless communication system. A demodulatorperforms this operation through an auto gain control (hereinafterreferred to as “AGC”) circuit. In order to adjust the amplitude of areceived signal to within a dynamic range, the AGC circuit sends an AGCpreamble signal before a signal such as a start symbol at the start of apacket and the AGC circuit controls an amplification gain based on thereception level of this preamble signal. The AGC preamble signal isdesigned to be sent by being inserted in a transmission signal togetherwith data. An AGC error is an error between a target value of thereception level after AGC and actual reception level.

However, in a conventional transmission apparatus and gain controlmethod, when appropriate AGC preambles cannot be set when, for example,the channel quality is poor, an AGC pull-in characteristic deteriorates,the signal may be clipped or the reception level may decrease, andquantization errors may increase, making it difficult to demodulate thereceived signal without errors. Furthermore, since AGC preambles are notdata that is sent to the party on the other end, there is a problem thatinserting AGC preambles deteriorates data transmission efficiency.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a transmissionapparatus and auto gain control method which can make transmissionefficiency compatible with an error rate characteristic.

This object can be attained by comparing a transmission time interval atwhich a transmission signal is sent to the party on the other end with athreshold, increasing the number of AGC preambles when the transmissiontime interval is equal to or greater than the threshold and setting thenumber of AGC preambles to a normal number when the transmission timeinterval is smaller than the threshold to adaptively change the numberof AGC preambles according to the transmission time interval.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a transmissionapparatus according to Embodiment 1 of the present invention;

FIG. 2 is a block diagram showing a configuration of a receptionapparatus according to Embodiment 1 of the present invention;

FIG. 3 is a flow chart showing an operation of a transmission apparatusaccording to Embodiment 1 of the present invention;

FIG. 4 illustrates a frame format with five AGC preambles;

FIG. 5 illustrates a frame format with ten AGC preambles;

FIG. 6 is a block diagram showing a configuration of a transmissionapparatus according to Embodiment 2 of the present invention;

FIG. 7 is a block diagram showing a configuration of a transmissionapparatus according to Embodiment 3 of the present invention;

FIG. 8 is a block diagram showing a configuration of a receptionapparatus according to Embodiment 3 of the present invention;

FIG. 9 is a block diagram showing a configuration of a transmissionapparatus according to Embodiment 4 of the present invention;

FIG. 10 is a block diagram showing a configuration of a base stationapparatus to which a transmission apparatus according to Embodiment 5 ofthe present invention is applied;

FIG. 11 is a block diagram showing a configuration of a mobile stationapparatus to which the transmission apparatus according to Embodiment 5of the present invention is applied; and

FIG. 12 illustrates a frame format.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below.

Embodiment 1

FIG. 1 illustrates a configuration of a transmission apparatus 100according to Embodiment 1 of the present invention and FIG. 2illustrates a configuration of a reception apparatus 200 according toEmbodiment 1 of the present invention.

The transmission apparatus 100 is mainly constructed of a transmissioncontrol section 101, a coding section 102, a modulation section 103, apreamble insertion section 104, a transmission section 105, an antenna106, a counter section 107, a delay section 108, a subtraction section109 and a preamble number control section 110.

The reception apparatus 200 is mainly constructed of an antenna 201, areception section 202, a synchronization section 203, a demodulationsection 204, a decoding section 205, a reception control section 206 andan AGC section 207.

First, the configuration of the transmission apparatus 100 will beexplained using FIG. 1.

The transmission control section 101 temporarily stores a transmissionsignal and outputs the transmission signal to the coding section 102 ata transmission timing. Furthermore, the transmission control section 101decides the transmission timing, generates a transmission timing signaland outputs the generated transmission timing signal to the countersection 107. Here, transmission is carried out once per frame.

The coding section 102 carries out coding processing on the transmissionsignal input from the transmission control section 101 and outputs thecoded transmission signal to the modulation section 103.

The modulation section 103 modulates the transmission signal input fromthe coding section 102 and outputs the modulated signal to the preambleinsertion section 104. When an OFDM scheme is applied as thecommunication scheme, the modulation section 103 performs signal mappingsuch as QPSK or 16QAM on the transmission signal, then applies aninverse fast Fourier transform (IFFT) processing and performs orthogonalfrequency division multiplexing on the transmission signal. On the otherhand, when a CDMA scheme is applied as the communication scheme, themodulation section 103 carries out signal mapping such as QPSK or 16QAMon the transmission signal and then applies spreading processing.

The preamble insertion section 104 inserts various preambles such as AGCpreamble number and propagation path estimation preamble into thetransmission signal input from the modulation section 103 and outputsthe transmission signal to the transmission section 105. The preambleinsertion section 104 includes AGC preambles corresponding to the numberdetermined by the preamble number control section 110 in thetransmission signal and outputs the transmission signal to thetransmission section 105.

The transmission section 105 converts the frequency of the transmissionsignal input from the preamble insertion section 104 from a basebandfrequency to a radio frequency and transmits the transmission signalfrom the antenna 106.

The counter section 107 generates information indicating a transmissiontiming based on the transmission timing input from the transmissioncontrol section 101 which is a transmission interval measuring sectionand outputs the information to the delay section 108 and subtractionsection 109.

The delay section 108 delays the information indicating the transmissiontiming input from the counter section 107 and outputs the delayedinformation to the subtraction section 109.

The subtraction section 109 calculates a difference between thepreviously transmitted transmission timing and a transmission timing tobe transmitted this time (hereinafter described as “transmission timingdifference”) from the information indicating the transmission timinginput from the counter section 107 and the information indicating thetransmission timing input from the delay section 108 and outputs thecalculated transmission timing difference as a transmission timeinterval to the preamble number control section 110.

The preamble number control section 110 compares a threshold with thetransmission timing difference input from the subtraction section 109,adaptively determines the number of AGC preambles according to theresult of the comparison with the threshold and instructs the preambleinsertion section 104 to include the determined number of AGC preamblesin the transmission signal.

The transmission time interval may become equal to or higher than thethreshold in a case where the transmission time interval is long duringtransmission, a case where transmission is carried out first or a casewhere transmission in progress is interrupted once and then transmissionis resumed. Therefore, it is possible to set a greater number of AGCpreambles when transmission is carried out first than the number of AGCpreambles for the second and subsequent transmissions. Furthermore, itis also possible to set the greater number of AGC preambles whentransmission is resumed after a long period of interruption than thenumber of AGC preambles for the second and subsequent transmissionsafter transmission is resumed.

When the transmission time interval is equal to or greater than thethreshold, the preamble number control section 110 can continue toincrease the number of AGC preambles for a predetermined time after thetransmission is performed with the number of AGC preambles increased.The method of setting the number of AGC preambles will be describedlater.

Next, the configuration of the reception apparatus 200 will be explainedusing FIG. 2.

The reception section 202 converts the frequency of the signal receivedfrom the antenna 201 from a radio frequency to a baseband frequency andoutputs the signal to the synchronization section 203 and AGC section207.

The synchronization section 203 detects the reception timing from thereceived signal input from the reception section 202 and outputs thedetected reception timing to the demodulation section 204.

The demodulation section 204 demodulates the received signal input fromthe synchronization section 203 and outputs the demodulated signal tothe decoding section 205.

The decoding section 205 carries out decoding processing on the receivedsignal input from the demodulation section 204 and outputs the decodedsignal to the reception control section 206.

The reception control section 206 temporarily stores the received signalinput from the decoding section 205, detects whether there is an erroror not and outputs the received signal when there is no error.

The AGC section 207 generates an AGC control signal from the receivedsignal input from the reception section 202 and outputs the generatedAGC control signal to the reception section 202. That is, the AGCsection 207 performs control such that the reception level is keptconstant even when the communication distance varies between radiocommunication apparatuses such as a base station apparatus and acommunication terminal apparatus. Furthermore, the AGC section 207calculates the reception level and outputs the calculated receptionlevel as reception level information. The reception level informationis, for example, an RSSI (Received Signal Strength Indicator). Note thatthe reception level information is not limited to the RSSI but can alsobe any information other than RSSI.

Next, the operation of the transmission apparatus 100 will be explainedusing FIG. 3, FIG. 4 and FIG. 5. In FIG. 4 and FIG. 5, P1 to P10 denoteAGC preambles and D1 to D3 denote transmission data. First, thetransmission apparatus 100 counts a transmission timing using thecounter section 107, calculates a transmission timing difference usingthe subtraction section 109, compares the transmission time intervalwith a threshold using the preamble number control section 110 (step(hereinafter referred to as “ST”) ST301). When the transmission timeinterval is smaller than the threshold, it is decided that five AGCpreambles are inserted and the preamble insertion section 104 insertsfive AGC preambles as shown in FIG. 4 (ST302). On the other hand, whenit is decided in ST301 that the transmission time interval is equal toor greater than the threshold, it is decided that ten AGC preambles areinserted, and the preamble insertion section 104 inserts ten AGCpreambles as shown in FIG. 5 (ST303) Next, the transmission section 105converts the frequency of the transmission signal from a basebandfrequency to a radio frequency and transmits the converted signal fromthe antenna 106 (ST304).

Thus, according to the transmission apparatus and auto gain controlmethod of this embodiment, the number of AGC preambles is adaptivelychanged according to the transmission timing difference, and thereforewhen the transmission time interval is long, the number of AGC preamblesis increased to improve the error rate characteristic, and when thetransmission time interval is short, the number of AGC preambles isreduced to give priority to the transmission efficiency, and thereforeit is possible to prevent degradation of a pull-in characteristic due toauto gain control and make the transmission efficiency compatible withthe error rate characteristic.

Embodiment 2

FIG. 6 illustrates the configuration of a transmission apparatus 600according to Embodiment 2 of the present invention. This embodiment ischaracterized in that the number of AGC preambles is changed accordingto the reception level. FIG. 6 differs from FIG. 1 in that a selectionsection 601 is provided. The same components as those in FIG. 1 areassigned the same reference numerals and explanations thereof will beomitted. Furthermore, the reception apparatus in this embodiment has thesame configuration as that in FIG. 2, and therefore explanations thereofwill be omitted.

Based on reception level information input from an AGC section 207 whichis a reception level measuring section and an initial value of the AGCgain, the selection section 601 calculates the difference between thereception level information and the initial value of the AGC gain,compares the calculated difference with a threshold (not shown) anddetermines the number of AGC preambles according to the comparisonresult. That is, when the difference between the reception levelinformation and the initial value of the AGC gain is smaller than thethreshold, the time required to converge AGC is shorter, and thereforethe selection section 601 selects threshold α (threshold α>threshold β)so as to reduce the number of AGC preambles and when the differencebetween the reception level information and the initial value of the AGCgain is equal to or greater than the threshold, the time required toconverge AGC is longer, and therefore the selection section 601 selectsthreshold β so as to increase the number of AGC preambles. Note that theoperation of the transmission apparatus 600 is the same as that in FIG.3 except that a threshold used by the preamble number control section110 is selected based on the reception level information and AGC initialvalue, and therefore explanations thereof will be omitted.

Thus, according to the transmission apparatus and auto gain controlmethod of this embodiment, in addition to the effects of Embodiment 1,the time required for AGC pulling-in is estimated according to not onlythe transmission time interval but also the difference between thereception level information and the initial value of the AGC gain to setthe number of AGC preambles, and therefore it is possible to set thenumber of AGC preambles in a more meticulous manner according to thechannel situation with the party on the other end and further make thetransmission efficiency compatible with the error rate characteristic.

Embodiment 3

FIG. 7 illustrates a configuration of a transmission apparatus 700according to Embodiment 3 of the present invention and FIG. 8illustrates a configuration of a reception apparatus 800 according toEmbodiment 3 of the present invention. This embodiment is characterizedin that the number of AGC preambles is changed also in consideration ofwhether the distance from the party on the other end is increasing orreducing from that at time of the previous transmission using a historyof reception level information. In this embodiment, FIG. 7 differs fromFIG. 1 in that a selection section 701 is provided and the configurationincluding a selection section 801, a memory 802, a memory 803 and acomparison section 804 in FIG. 8 differs from that in FIG. 2. The samecomponents as those in FIG. 1 and FIG. 2 are assigned the same referencenumerals and explanations thereof will be omitted.

The selection section 701 selects either threshold α or threshold β(threshold α>threshold β) according to information input from thecomparison section 804 as to whether the party on the other end ismoving away or moving closer and outputs the selected thresholdinformation to the preamble number control section 110. The AGC gain isgenerally increased when the distance from the party on the other endincreases from that at the time of the previous communication. On theother hand, when the distance from the party on the other end decreasesfrom that at the time of the previous communication, the AGC gain isreduced. The change rate is higher when the AGC is increased than whenthe AGC is decreased. For this reason, the selection section 701 setsthreshold α when the distance from the party on the other end increasesfrom that at the time of the previous communication and sets threshold βwhen the distance from the party on the other end decreases from that atthe time of the previous communication. When an RSSI is used asreception level information, it is also possible to select threshold αor threshold β according to the change rate of the RSSI.

The selection section 801 outputs reception level information input fromthe AGC section 207 to the memory 802 and memory 803 alternately.

The memory 802 stores the reception level information input from theselection section 801 and outputs the reception level information to thecomparison section 804. The timing at which the information is output tothe comparison section 804 is the time at which the reception levelinformation is stored in both the memory 802 and memory 803.

The memory 803 stores the reception level information input from theselection section 801 and outputs the reception level information to thecomparison section 804. The timing at which the information is output tothe comparison section 804 is the time at which the reception levelinformation is stored in both the memory 802 and memory 803.

The comparison section 804 compares the respective pieces of thereception level information input from the memory 802 and memory 803,detects whether the change of the reception level information isincreasing or decreasing and outputs the detection result to theselection section 701. The operation of the transmission apparatus 700is the same as that in FIG. 3 except that the threshold used in thepreamble number control section 110 is made variable, and thereforeexplanations thereof will be omitted.

As another method of selecting a threshold using reception levelinformation at the selection section 701, it is also possible to selecta threshold through extrapolation using past reception levelinformation. In this case, when the channel condition changesdrastically because the party on the other end is moving at a highspeed, it is possible to set an appropriate number of AGC preambles on acase-by-case basis.

In this way, according to the transmission apparatus and auto gaincontrol method of this embodiment, in addition to the effects ofEmbodiment 1, the number of AGC preambles is changed in consideration ofnot only the transmission time interval but also whether the terminal ismoving away or moving closer, and therefore it is possible to set thenumber of AGC preambles in a more meticulous manner according to thechannel situation, etc., with the party on the other end and furthermake the transmission efficiency compatible with the error ratecharacteristic. Furthermore, the number of AGC preambles is determinedaccording to the history of the reception levels, and therefore when thenumber takes an outstandingly different value temporarily due totemporary degradation of the communication environment and it is notnecessary to increase the number of AGC preambles urgently, it ispossible to prevent the transmission efficiency from being reduced byincreasing the number of AGC preambles.

In this embodiment, the selection section 701 selects a threshold fromtwo thresholds α and β, but the number of thresholds that can beselected by the selection section 701 is not limited to the twothresholds α and β and the threshold can be selected from among anarbitrary number of thresholds. Furthermore, this embodiment storesreception levels corresponding to past two times in the memories 802,803 and decides whether the party on the other end is moving away ormoving closer, but the present invention is not limited to the casewhere reception levels corresponding to past two times are stored in thememories 802, 803 and it is decided whether the party on the other endis moving away or moving closer, and the present invention can also beadapted so that reception levels of past three or more times are storedin memory and it is decided whether the party on the other end is movingaway or moving closer. In this case, the number of memories can be threeor more. Furthermore, the comparison section 804 can decide whether theparty on the other end is moving at a high speed or low speed, andtherefore when the party on the other end is moving at a high speed, itis possible to increase the number of AGC preambles and fix the numberto that value. Furthermore, this embodiment selects threshold α orthreshold β by subtracting the reception level information and decidingwhether the party on the other end is moving away or moving closer, butthe present invention is not limited to the case where threshold α orthreshold α is selected by subtracting the reception level informationand deciding whether the party on the other end is moving away or movingcloser and the present invention can also be adapted so that receptionlevel information is averaged and the averaged reception levelinformation is used to select threshold α or threshold β.

Embodiment 4

FIG. 9 illustrates a configuration of a transmission apparatus 900according to Embodiment 4 of the present invention. This embodiment ischaracterized in that threshold α or threshold β is selected based onthreshold setting information such as channel quality information inputfrom a transmission control section to a selection section. In thisembodiment, FIG. 9 differs from FIG. 1 in the configuration in which aselection section 901 is provided. The same components as those in FIG.1 are assigned the same reference numerals and explanations thereof willbe omitted. Furthermore, the reception apparatus has the sameconfiguration as that in FIG. 2, and therefore explanations thereof willbe omitted.

A transmission control section 101 temporarily stores threshold settinginformation for selecting threshold α or threshold β input from areception section (not shown) or threshold setting information notifiedfrom the party on the other end and outputs the threshold settinginformation to the selection section 901 at a timing at whichtransmission timing information is output. Generally, in the case of anFDD (Frequency Division Duplex) scheme, the transmission control section101 is notified of threshold setting information from a mobile stationand stores the notified threshold setting information. On the otherhand, in the case of a TDD (Time Division Duplex) scheme, thetransmission control section 101 stores threshold setting informationdetected at the time of reception. The type of threshold settinginformation will be described later.

The selection section 901 selects either threshold α or threshold βbased on the threshold setting information input from the transmissioncontrol section 101 and outputs the selected threshold to the preamblenumber control section 110.

Next, the type of threshold setting information output from thetransmission control section 101 to the selection section 901 will beexplained.

First threshold setting information is channel quality. That is, theselection section 901 selects threshold β when channel qualityinformation indicating poor channel quality is input from thetransmission control section 101 and selects threshold α when channelquality information indicating good channel quality is input from thetransmission control section 101. By so doing, if channel qualitydeteriorates, the number of AGC preambles is increased even if thetransmission time interval of a transmission signal is relatively short,and therefore it is possible to prevent degradation of an error ratecharacteristic even if the channel quality deteriorates.

Second threshold setting information is a multipath delay time. That is,the selection section 901 selects threshold β when informationindicating that the multipath delay time is large is input from thetransmission control section 101 and selects threshold α wheninformation indicating that the multipath delay time is small is inputfrom the transmission control section 101. By so doing, if the multipathdelay time is large, the number of AGC preambles is increased even ifthe transmission time interval of a transmission signal is relativelyshort, and therefore it is possible to prevent degradation of the errorrate characteristic even if the delay time is large.

Third threshold setting information is the moving speed of a terminal.That is, the selection section 901 selects threshold β when terminalinformation with a high moving speed is input from the transmissioncontrol section 101 and selects threshold α when terminal informationwith a low moving speed is input from the transmission control section101. By so doing, if the moving speed of the terminal increases, thenumber of AGC preambles is increased even if the transmission timeinterval of a transmission signal is relatively short, and therefore itis possible to prevent degradation of the error rate characteristic evenif the moving speed of the terminal increases.

Fourth threshold setting information is a band usage situation. That is,the selection section 901 selects threshold β when band informationindicating that there is a sufficient space in the band is input fromthe transmission control section 101 and selects threshold α when bandinformation indicating that there is not a sufficient space in the bandis input from the transmission control section 101. Whether there is asufficient space in the band or not may also be determined based onwhether the ratio of the band used for communication with the party onthe other end to a maximum allowable band is equal to or greater than athreshold or may be determined using other methods. When there is asufficient space in the band in use, the number of AGC preambles isincreased, and therefore it is possible to further improve the errorrate characteristic without sacrificing the transmission efficiency. Theoperation of the transmission apparatus 900 is the same as that in FIG.3 except that the threshold is variable, and therefore explanationsthereof will be omitted.

Thus, according to the transmission apparatus and auto gain controlmethod of this embodiment, in addition to the effects of Embodiment 1,the number of AGC preambles is changed in consideration of not only thetransmission time interval but also various types of threshold settinginformation, and therefore it is possible to set the number of AGCpreambles in a more meticulous manner according to the channelsituation, etc., with the party on the other end and further make thetransmission efficiency compatible with error rate characteristic.

Embodiment 5

FIG. 10 illustrates a configuration of a base station apparatus 1000 towhich a transmission apparatus according to Embodiment 5 of the presentinvention is applied and FIG. 1 illustrates a configuration of a mobilestation 1100 which is a communication terminal apparatus according toEmbodiment 5 of the present invention. This embodiment is characterizedin that the number of AGC preambles at a mobile station set by a basestation apparatus is notified from the base station apparatus to themobile station. In this embodiment, the configuration in FIG. 10provided with a preamble information insertion section 1001 differs fromthat in FIG. 1. The same components as those in FIG. 1 are assigned thesame reference numerals and explanations thereof will be omitted.Furthermore, the reception apparatus has the same configuration as thatin FIG. 2, and therefore explanations thereof will be omitted.

The base station apparatus 1000 controls a plurality of mobile stations1100 in a concentrated manner and controls which mobile station carriesout transmission. Therefore, the base station apparatus 1000 canrecognize transmission intervals of the respective mobile stations 1100.

A preamble number control section 110 compares a threshold with atransmission timing difference input from a subtraction section 109,adaptively decides the number of AGC preambles according to the resultof the comparison with the threshold and outputs the number of AGCpreambles decided as preamble number information at the respectivemobile stations 1100 to the preamble information insertion section 1001.

The preamble information insertion section 1001 which is a notificationsection inserts the preamble number information input from the preamblenumber control section 110 into the transmission signal input from themodulation section 103 and outputs the transmission signal to thetransmission section 105.

The preamble number control section 110 at the mobile station 1100 setsthe number of AGC preambles set by the base station apparatus 1000according to the preamble number information extracted from the receivedsignal as is and instructs a preamble insertion section 104 to insertthe set number of AGC preambles into the transmission signal.

Thus, according to the transmission apparatus and gain control method ofthis embodiment, a variable number of AGC preambles notified from thebase station apparatus are inserted into the transmission signal, andtherefore it is possible to prevent degradation of an AGC pull-incharacteristic and make the transmission efficiency compatible with theerror rate characteristic. Furthermore, the mobile station inserts AGCpreambles corresponding to the number of AGC preambles notified from thebase station apparatus into the transmission signal as they are and neednot calculate the number of AGC preambles, and can thereby increase theprocessing speed.

In this embodiment, the number of AGC preambles set by the base stationapparatus 1000 can be set by arbitrarily selecting any one of themethods described in Embodiments 1 to 4.

Other Embodiments

The method of controlling the number of AGC preambles in a case where atransmission signal has a frame format including a random access channelwill be explained using FIG. 12.

A channel through which a terminal, etc., carries out transmissionrandomly is generally called a “random access channel.” A frame formatincluding a random access channel is used, for example, for MMAC orBRAN. The number of AGC preambles in such a random access channel isincreased to 10 and fixed to that number.

As another example where the number of AGC preambles is increased andfixed to that number, when data for which good channel quality isrequired such as retransmission data or control data is transmitted, thenumber of AGC preambles is increased to 10 and fixed to that number.

Furthermore, the transmission apparatuses described in Embodiments 1 to5 can be used for both an uplink and downlink. When the number of AGCpreambles is changed on the downlink, there may be users who carry outinitial synchronization pulling-in, and therefore the initialsynchronization pull-in characteristic may deteriorate for such users.For this reason, it is also effective to apply a change in the number ofAGC preambles only to transmission apparatuses which transmit on theuplink. When the transmission apparatus described in each of the abovedescribed embodiments is applied only to a transmission apparatus whichcarries out transmission on the uplink, users who carry out initialsynchronization pulling-in on the downlink can prevent the error ratecharacteristic from deteriorating.

Furthermore, in Embodiments 1 to 5, the transmission apparatus canchange the number of AGC preambles from one party on the other end toanother.

Furthermore, Embodiments 1 to 5 have assumed that the number of AGCpreambles in the case with many AGC preambles is 10 and the ordinarynumber of AGC preambles is 5, but the present invention is not limitedto the case where the number of AGC preambles in the case with many AGCpreambles is 10 and the ordinary number of AGC preambles is 5 and can beadapted so that the number of AGC preambles in the case with many AGCpreambles is set to any number other than 10 and the ordinary number ofAGC preambles is set to any number other than 5. In short, any number isacceptable if the number of AGC preambles in the case with many AGCpreambles is at least greater than the ordinary number of AGC preambles.

Furthermore, the transmission apparatus described in each of theforegoing embodiments can be applied to a base station apparatus and acommunication terminal apparatus.

Furthermore, a transmission signal transmitted by the transmissionapparatuses according to Embodiments 1 to 5 or other embodiments can beof a preamble format in an OFDM communication scheme or BRAN (BroadbandRadio Access Networks) system, or without being limited to the OFDMcommunication scheme or BRAN system, the transmission signal can be of apreamble format according to a communication scheme other than an OFDMcommunication scheme or BRAN system.

Furthermore, in Embodiments 1 to 5 or other embodiments, the number ofAGC preambles is set by comparing the transmission time interval orreception level, etc., with a threshold, but the present invention isnot limited to the case of setting the number of AGC preambles bycomparing the transmission time interval or reception level, etc., witha threshold and can use any method such as a method of determining thenumber of AGC preambles through calculations.

As described above, the present invention can make the transmissionefficiency compatible with the error rate characteristic.

This application is based on the Japanese Patent Application No.2002-325225 filed on Nov. 8, 2002, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is preferably applicable to a transmissionapparatus and auto gain control method for transmitting a transmissionsignal including auto gain control preambles.

[FIG. 1]

-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   104 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   107 COUNTER SECTION-   108 DELAY SECTION-   109 SUBTRACTION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   THRESHOLD    [FIG. 2]-   RECEIVED SIGNAL-   206 RECEPTION CONTROL SECTION-   205 DECODING SECTION-   204 DEMODULATION SECTION-   203 SYNCHRONIZATION SECTION-   202 RECEPTION SECTION-   207 AGC SECTION-   RECEPTION LEVEL INFORMATION    [FIG. 3]-   START-   ST301 TRANSMISSION TIME INTERVAL≧THRESHOLD?-   ST302 INSERT FIVE AGC PREAMBLES-   ST303 INSERT TEN AGC PREAMBLES-   ST304 TRANSMIT-   END    [FIG. 6]-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   104 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   107 COUNTER SECTION-   108 DELAY SECTION-   109 SUBTRACTION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   601 SELECTION SECTION-   RECEPTION LEVEL IFNORMATION-   THRESHOLD α-   THRESHOLD β-   INITIAL VALUE OF AGC GAIN    [FIG. 7]-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   104 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   107 COUNTER SECTION-   108 DELAY SECTION-   109 SUBTRACTION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   701 SELECTION SECTION-   FROM COMPARISON SECTION 804-   THRESHOLD α-   THRESHOLD β    [FIG. 8]-   RECEIVED SIGNAL-   206 RECEPTION CONTROL SECTION-   205 DECODING SECTION-   204 DEMODULATION SECTION-   203 SYNCHRONIZATION SECTION-   202 RECEPTION SECTION-   TO SELECTION SECTION 701-   804 COMPARISON SECTION-   802 MEMORY-   803 MEMORY-   801 SELECTION SECTION-   RECEPTION LEVEL INFORMATION-   207 AGC SECTION    [FIG. 9]-   THRESHOLD SETTING INFORMATION-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   104 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   107 COUNTER SECTION-   108 DELAY SECTION-   109 SUBTRACTION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   901 SELECTION SECTION-   THRESHOLD α-   THRESHOLD β    [FIG. 10]-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   1001 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   107 COUNTER SECTION-   108 DELAY SECTION-   109 SUBTRACTION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   THRESHOLD    [FIG. 11]-   TRANSMISSION SIGNAL-   101 TRANSMISSION CONTROL SECTION-   102 CODING SECTION-   103 MODULATION SECTION-   104 PREAMBLE INSERTION SECTION-   105 TRANSMISSION SECTION-   110 PREAMBLE NUMBER CONTROL SECTION-   PREAMBLE NUMBER INFORMATION    [FIG. 12]-   NOTIFICATION CHANNEL-   DOWNLINK-   UPLINK-   RANDOM ACCESS CHANNEL

1. A transmission apparatus comprising: a preamble insertion sectionthat inserts auto gain control preambles into a transmission signal; anda preamble number control section that adaptively controls the number ofauto gain control preambles inserted by said preamble insertion sectionaccording to a transmission time interval of said transmission signal.2. The transmission apparatus according to claim 1, wherein saidpreamble number control section increases the number of auto gaincontrol preambles at the time of first transmission by the party on theother end.
 3. The transmission apparatus according to claim 1, whereinsaid preamble number control section increases said number of auto gaincontrol preambles in the case of a plurality of transmissionsimmediately after transmission is carried out with said number of autogain control preambles increased.
 4. The transmission apparatusaccording to claim 1, wherein when the reception level is close to aninitial value during auto gain control, said preamble number controlsection reduces said number of auto gain control preambles compared tothe case where the reception level is far from said initial value. 5.The transmission apparatus according to claim 1, wherein said preamblenumber control section decides whether the party on the other end ismoving away or moving closer, based on the received signal, reduces thenumber of auto gain control preambles when said party on the other endis moving away and increases the number of auto gain control preambleswhen said party on the other end is moving closer.
 6. The transmissionapparatus according to claim 1, wherein said preamble number controlsection sets a variable threshold and increases, when said transmissiontime interval is equal to or greater than said threshold, said number ofauto gain control preambles compared to the case where said transmissiontime interval is smaller than said threshold.
 7. The transmissionapparatus according to claim 1, wherein said transmission signal istransmitted only on an uplink.
 8. The transmission apparatus accordingto claim 1, wherein when said transmission signal includes data forwhich high channel quality is required, said preamble number controlsection is fixed to a state with a high number of auto gain controlpreambles.
 9. The transmission apparatus according to claim 1, whereinsaid preamble number control section changes said number of auto gaincontrol preambles according to channel quality.
 10. The transmissionapparatus according to claim 1, wherein said preamble number controlsection changes said number of auto gain control preambles according toa delay time of said transmission signal.
 11. The transmission apparatusaccording to claim 1, wherein said preamble number control sectionchanges said number of auto gain control preambles according to themoving speed of the party on the other end.
 12. The transmissionapparatus according to claim 1, wherein said preamble number controlsection changes said number of auto gain control preambles according tothe bandwidth used.
 13. The transmission apparatus according to claim 1,wherein said preamble number control section changes said number of autogain control preambles using reception level information obtained in thepast.
 14. The transmission apparatus according to claim 1, wherein saidpreamble number control section changes said number of auto gain controlpreambles using reception level information obtained by extrapolation.15. The transmission apparatus according to claim 1, wherein saidpreamble number control section fixes said number of auto gain controlpreambles inserted into said transmission signal to be transmitted tothe party on the other end having poor channel quality to a state with ahigh number of auto gain control preambles.
 16. The transmissionapparatus according to claim 1, wherein said preamble number controlsection fixes said number of auto gain control preambles inserted intosaid transmission signal to be transmitted to the party on the other endin an environment with a large multipath delay time to a state with ahigh number of auto gain control preambles.
 17. The transmissionapparatus according to claim 1, wherein said preamble number controlsection fixes said number of auto gain control preambles inserted intosaid transmission signal to be transmitted to the party on the other endmoving at a high speed to a state with a high number of auto gaincontrol preambles.
 18. The transmission apparatus according to claim 1,wherein when there is a sufficient space in the bandwidth used, saidpreamble number control section fixes said number of auto gain controlpreambles inserted into said transmission signal to a state with a highnumber of auto gain control preambles.
 19. The transmission apparatusaccording to claim 1, wherein when the frame format of said transmissionsignal includes a random access channel, said preamble number controlsection fixes said number of auto gain control preambles to a state witha high number of auto gain control preambles.
 20. A base stationapparatus comprising a transmission apparatus, said transmissionapparatus comprising: a preamble insertion section that inserts autogain control preambles into a transmission signal; and a preamble numbercontrol section that adaptively controls the number of auto gain controlpreambles inserted by said preamble insertion section according to atransmission time interval of said transmission signal.
 21. Acommunication terminal apparatus comprising a transmission apparatus,said transmission apparatus comprising: a preamble insertion sectionthat inserts auto gain control preambles into a transmission signal; anda preamble number control section that adaptively controls the number ofauto gain control preambles inserted by said preamble insertion sectionaccording to a transmission time interval of said transmission signal.22. A communication system comprising: a base station apparatus providedwith a preamble number control section that controls the number of autogain control preambles to be inserted into a transmission signal at acommunication terminal apparatus according to a transmission timeinterval of said transmission signal and a notification section thatnotifies said number of auto gain control preambles to saidcommunication terminal apparatus; and a communication terminal apparatusprovided with an insertion section that inserts auto gain controlpreambles corresponding to said number of auto gain control preamblesnotified by said notification section into the transmission signal. 23.An auto gain control method comprising: a step of measuring atransmission time interval of a transmission signal; a step ofadaptively determining the number of auto gain control preamblesaccording to said transmission time interval; a step of inserting saiddetermined number of auto gain control preambles into the transmissionsignal; a step of transmitting said transmission signal including theauto gain control preambles to the party on the other end; and a step ofsaid party on the other end carrying out auto gain control based on saidauto gain control preambles.